Fluoride ion battery and method for producing fluoride ion battery

ABSTRACT

An object of the present disclosure is to provide a fluoride ion battery of which power generating elements (a cathode active material layer, a solid electrolyte layer, and an anode active material layer) may be formed by two kinds of members: an electrode layer and a solid electrolyte layer. The present disclosure achieves the object by providing a fluoride ion battery comprising: an electrode layer that includes a first metal element or a carbon element and has capability of fluorination and defluorination; a solid electrolyte layer containing a solid electrolyte material, the solid electrolyte material including a second metal element with lower fluorination potential and defluorination potential than the potentials of the first metal element or the carbon element; and an anode current collector, in this order; and an anode active material layer being not present between the solid electrolyte layer and the anode current collector.

TECHNICAL FIELD

The present disclosure relates to a fluoride ion battery and a methodfor producing the fluoride ion battery.

BACKGROUND ART

As high-voltage and high-energy density batteries, for example, Li ionbatteries are known. The Li ion battery is a cation-based batteryutilizing Li ions as the carrier. Meanwhile, as anion-based batteries,fluoride ion batteries utilizing fluoride ions as the carrier are known.For example, Patent Literature 1 discloses an electrochemical cell(fluoride ion battery) provided with a cathode, an anode, and anelectrolyte that can conduct an anion charge carrier (F⁻).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application Laid-Open (JP-A)    No. 2013-145758

SUMMARY OF DISCLOSURE Technical Problem

In a general fluoride ion battery, 5 kinds of members: a cathode currentcollector, a cathode active material layer, an electrolyte layer, ananode active material layer, and an anode current collector, are used.On the other hand, in light of reducing cost of a battery, for example,a battery having a simple structure is preferable. The presentdisclosure has been made in view of the above circumstances, and a mainobject thereof is to provide a fluoride ion battery of which powergenerating elements (a cathode active material layer, a solidelectrolyte layer, and an anode active material layer) may be formed bytwo kinds of members: an electrode layer and a solid electrolyte layer.

Solution to Problem

In order to achieve the object, the present disclosure provides afluoride ion battery comprising: an electrode layer that includes afirst metal element or a carbon element and has capability offluorination and defluorination; a solid electrolyte layer containing asolid electrolyte material, the solid electrolyte material including asecond metal element with lower fluorination potential anddefluorination potential than the potentials of the first metal elementor the carbon element; and an anode current collector, in this order;and an anode active material layer being not present between the solidelectrolyte layer and the anode current collector.

According to the present disclosure, the specific two kinds of members,an electrode layer and a solid electrolyte layer, may form the powergenerating elements of a fluoride ion battery.

In the disclosure, the anode current collector may be directly disposedon a surface of the solid electrolyte layer.

Also, the present disclosure provides a fluoride ion battery comprising:an electrode layer that includes a first metal element or a carbonelement and has capability of fluorination and defluorination; a solidelectrolyte layer containing a solid electrolyte material, the solidelectrolyte material including a second metal element with lowerfluorination potential and defluorination potential than the potentialsof the first metal element or the carbon element; and an anode currentcollector, in this order; and a fluoride layer containing a fluoride ofthe first metal element or the carbon element on a surface, that is theanode current collector side, of the electrode layer; and an anodeactive material layer containing a simple substance of the second metalelement on a surface, that is the anode current collector side, of thesolid electrolyte layer.

According to the present disclosure, the specific two kinds of members,an electrode layer and a solid electrolyte layer, may form the powergenerating elements of a fluoride ion battery.

In the disclosure, the anode current collector may be the same member asthe electrode layer.

In the disclosure, the fluoride ion battery may further comprise abipolar structure in which a plurality of the electrode layers and thesolid electrolyte layers are alternately disposed.

In the disclosure, the first metal element may be at least one kind ofPb, Cu, Sn, In, Bi, Sb, Ni, Co, La, Ce, Mn, V, Fe, Cr, Nb, Ti, and Zn.

In the disclosure, the second metal element may be at least one kind ofLa, Ba, Pb, Sn, Ca, and Ce.

In the disclosure, the solid electrolyte material may be at least onekind of La_(1-x)Ba_(x)F_(3-x) in which 0≤x≤2, Pb_(2-x)Sn_(x)F₄ in which0≤x≤2, Ca_(2-x)Ba_(x)F₄ in which 0≤x≤2, and Ce_(1-x)Ba_(x)F_(3-x) inwhich 0≤x≤2.

Also, the present disclosure provides a method for producing a fluorideion battery, the method comprising: a laminated body forming step offorming a laminated body including: an electrode layer that includes afirst metal element or a carbon element and has capability offluorination and defluorination; a solid electrolyte layer containing asolid electrolyte material, the solid electrolyte material including asecond metal element with lower fluorination potential anddefluorination potential than the potentials of the first metal elementor the carbon element; and an anode current collector, in this order;and an anode active material layer being not present between the solidelectrolyte layer and the anode current collector.

According to the present disclosure, a fluoride ion battery, of whichpower generating elements may be formed by the combination of thespecific electrode layer and solid electrolyte layer, may be obtained.

In the disclosure, the method may further comprise a charging step ofcharging the laminated body, forming a fluoride layer containing afluoride of the first metal element or the carbon element on a surface,that is the anode current collector side, of the electrode layer, andforming an anode active material layer containing a simple substance ofthe second metal element on a surface, that is the anode currentcollector side, of the solid electrolyte layer.

Advantageous Effects of Disclosure

The present disclosure exhibits effects such as a fluoride ion batteryof which power generating elements may be formed from two kinds ofmembers: an electrode layer and a solid electrolyte layer.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are schematic cross-sectional views exemplifying thefluoride ion battery of the present disclosure.

FIGS. 2A and 2B are schematic cross-sectional views exemplifying thefluoride ion battery of the present disclosure.

FIGS. 3A to 3D are schematic cross-sectional views exemplifying themethod for producing the fluoride ion battery of the present disclosure.

FIG. 4 is the result of a charge and discharge test for the evaluationcell obtained in Example 1.

DESCRIPTION OF EMBODIMENTS

The fluoride ion battery and the method for producing the fluoride ionbattery of the present disclosure will be hereinafter described indetail.

A. Fluoride Ion Battery

FIGS. 1A and 1B are schematic cross-sectional views exemplifying thefluoride ion battery of the present disclosure. FIG. 1A shows the statebefore charge, and FIG. 1B shows the state after charge. Fluoride ionbattery 10 shown in FIGS. 1A and 1B each comprises electrode layer 1that includes a first metal element or a carbon element and hascapability of fluorination and defluorination; solid electrolyte layer 2containing a solid electrolyte material, the solid electrolyte materialincluding a second metal element with lower fluorination potential anddefluorination potential than the potentials of the first metal elementor the carbon element; and anode current collector 3, in this order inthe thickness direction.

In fluoride ion battery 10 shown in FIG. 1A, an anode active materiallayer is not present between solid electrolyte layer 2 and anode currentcollector 3. In FIG. 1A, electrode layer 1 is directly disposed on onesurface of solid electrolyte layer 2, and anode current collector 3 isdirectly disposed on the other surface of solid electrolyte layer 2.Here, when electrode layer 1 is a Pb foil, and solid electrolyte layer 2is La_(0.9)Ba_(0.1)F_(2.9) (solid electrolyte material), and if thefluoride ion battery 10 shown in FIG. 1A were charged, the fluorinationreaction of electrode layer 1 (Pb foil) would occur in the interfacebetween electrode layer 1 and solid electrolyte layer 2, and therebyPbF₂ would be obtained. The PbF₂ corresponds to a charged cathode activematerial layer (fluoride layer 4). Incidentally, electrode layer 1 (Pbfoil) not in the reaction with fluoride ions may function as a cathodecurrent collector.

Meanwhile, in the interface between solid electrolyte layer 2 and anodecurrent collector 3, the defluorination reaction of solid electrolytelayer 2 (La_(0.9)Ba_(0.1)F_(2.9)) would occur, and thereby a simplesubstance of La would be generated(La_(0.9)Ba_(0.1)F_(2.9)+2.7e⁻→0.9La+0.1BaF₂+2.7F⁻). A simple substanceof La corresponds to a simple substance of the second metal element, andthe layer containing a simple substance of La corresponds to anodeactive material layer 5. It means that anode active material layer 5would be generated from solid electrolyte layer 2 in a self-formingmanner. In this manner, for example, power generating elements of abattery (a cathode active material layer, a solid electrolyte layer, andan anode active material layer) may be formed from the two kinds ofmembers: a Pb foil and La_(0.9)Ba_(0.1)F_(2.9).

Accordingly, obtained by charging fluoride ion battery 10 shown in FIG.1A is fluoride ion battery 10 comprising: fluoride layer 4 containing afluoride of the first metal element or the carbon element on a surface,that is anode current collector 3 side, of electrode layer 1; and anodeactive material layer 5 containing a simple substance of the secondmetal element on a surface, that is anode current collector 3 side, ofsolid electrolyte layer 2, as shown in FIG. 1B.

According to the present disclosure, the specific two kinds of members,an electrode layer and a solid electrolyte layer, may form the powergenerating elements of a fluoride ion battery. Reduction in the numberof the members used allows reduction in the cost of a battery. Also, theelectrode layer provides functions as both a current collector and acathode active material layer. Accordingly, it is unnecessary to useadditional member as a cathode current collector, and thus increasingenergy density of the battery is more achievable.

In particular, in the present disclosure, it has been found out thatpower generating elements of a battery (a cathode active material layer,a solid electrolyte layer, and an anode active material layer) may beformed by just the combination of an electrode layer with the solidelectrolyte layer which may be an anode active material layer by theself-forming reaction. Such a reaction mechanism is peculiar to afluoride ion all solid battery (a fluoride ion battery comprising asolid electrolyte layer), and is a reaction mechanism not conventionallyknown.

The fluoride ion battery of the present disclosure will be hereinafterdescribed in each constitution.

1. Electrode Layer

The electrode layer in the present disclosure is a layer that includes afirst metal element or a carbon element and has capability offluorination and defluorination. The first metal element or the carbonelement is usually fluorinated upon charge, and defluorinated upondischarge. A fluoride ion reacts with a lot of elements due to itsextremely high nucleophilicity, so that a fluoride is formed. Meanwhile,defluorination reaction is required to occur upon discharge in theelectrode layer. It means that the electrode layer is required to be alayer in which not only fluorination reaction but also defluorinationreaction may occur. Also, the electrode layer provides functions as botha current collector (or an intermediate current collector) and a cathodeactive material layer.

Examples of the electrode layer may include a metal electrode layerincluding the first metal element, and a carbon electrode layerincluding the carbon element. Examples of the metal electrode layer mayinclude a simple substance and an alloy, including the first metalelement. Examples of the first metal element may include at least onekind of Pb, Cu, Sn, In, Bi, Sb, Ni, Co, La, Ce, Mn, V, Fe, Cr, Nb, Tiand Zn. If the metal electrode layer is an alloy, the alloy may includeonly one kind of the first metal element, and may include two kinds ormore of the first metal elements. In the latter case, among a pluralityof the first metal elements, a metal element with the highestfluorination potential and defluorination potential (hereinafterreferred to as metal element A) is preferably the main component of thealloy. The proportion of the metal element A in the alloy may be 50 mol% or more, may be 70 mol % or more, and may be 90 mol % or more. Also,examples of the carbon electrode layer may include graphite andgraphene.

The thickness of the electrode layer before charge is, for example, 5 μmor more, and preferably 50 μm or more. If the thickness of the electrodelayer before charge is too small, the thickness of the portion thatfunctions as a current collector upon charge (the portion not in thereaction with fluoride ions) becomes small, and the sufficient currentcollecting function may not be possibly obtained. Incidentally theelectrode layer before charge refers to an electrode layer in which thefluoride layer containing a fluoride of the first metal element or thecarbon element is not present. Also, although the electrode layerfunctions as a cathode current collector, considering the corrosion dueto fluorination, an auxiliary current collector with high chemicalstability may be additionally arranged. Examples of the auxiliarycurrent collector may include a current collector including a noblemetal such as Au and Pt.

2. Solid Electrolyte Layer

The solid electrolyte layer in the present disclosure is a layercontaining a solid electrolyte material, the solid electrolyte materialincluding a second metal element with lower fluorination potential anddefluorination potential than the potentials of the first metal elementor the carbon element. The second metal element is usually deposited asa simple substance of metal upon charge, and fluorinated upon discharge.Also, a part of the solid electrolyte layer may become an anode activematerial layer by a self-forming reaction upon charge.

The solid electrolyte material is usually a material that has fluorideion conductivity and includes a second metal element and an F element.The second metal element has lower fluorination potential anddefluorination potential than those of the first metal element or thecarbon element. In other words, when the electrode layer includes afirst metal element, the second metal element has lower fluorinationpotential and defluorination potential than those of the first metalelement. Similarly, when the electrode layer includes a carbon element,the second metal element has lower fluorination potential anddefluorination potential than those of the carbon element. Thefluorination potential and the defluorination potential may be measuredby, for example, cyclic voltammetry (CV). The difference of thefluorination potential of the first metal element or the carbon elementfrom that of the second metal element is, for example, 0.05 V or more,and preferably 0.1 V or more. Also, the difference of the defluorinationpotential of the first metal element or the carbon element from that ofthe second metal element is, for example, 0.05 V or more, and preferably0.1 V or more.

Examples of the second metal element may include at least one kind ofLa, Ba, Pb, Sn, Ca, and Ce. The solid electrolyte material may includejust one kind of the second metal element, and may include two or morekinds thereof. In the latter case, among a plurality of the second metalelements, a metal element with the highest fluorination potential anddefluorination potential (hereinafter referred to as metal element B) ispreferably the main component among all the metal elements included inthe solid electrolyte material. The proportion of the metal element Bamong all the metal elements included in the solid electrolyte materialmay be 50 mol % or more, may be 70 mol % or more, and may be 90 mol % ormore.

Examples of the solid electrolyte material may include at least one kindof La_(1-x)Ba_(x)F_(3-x) in which 0≤x≤2, Pb_(2-x)Sn_(x)F₄ in which0≤x≤2, Ca_(2-x)Ba_(x)F₄ in which 0≤x≤2, and Ce_(1-x)Ba_(x)F_(3-x) inwhich 0≤x≤2. The x may be, respectively, larger than 0, may be 0.3 ormore, may be 0.5 or more, and may be 0.9 or more. Also, the x may be,respectively, smaller than 1, may be 0.9 or less, may be 0.5 or less,and may be 0.3 or less. The shape of the solid electrolyte material isnot limited, and examples thereof may include a granular shape.

The thickness of the solid electrolyte layer before charge is, forexample, 10 μm or more, and preferably 50 μm or more. Meanwhile, thethickness of the solid electrolyte layer before charge is, for example,300 μm or less. If the thickness of the solid electrolyte layer beforecharge is too small, short circuit may possibly easily occur, and if thethickness of the solid electrolyte layer before charge is too large,increasing the energy density of the battery may not possibly be easilyachieved. Incidentally, the solid electrolyte layer before charge refersto a solid electrolyte layer in which the anode active material layercontaining a simple substance of the second metal element is notpresent.

For example, as shown in FIG. 1A, fluoride ion battery 10 may notinclude an anode active material layer between solid electrolyte layer 2and anode current collector 3. Also, anode current collector 3 may bedirectly disposed on the surface of solid electrolyte layer 2.Similarly, electrode layer 1 may be directly disposed on the surface ofsolid electrolyte layer 2. Also, for example, as shown in FIG. 1B,fluoride ion battery 10 may comprise fluoride layer 4 containing afluoride of the first metal element or the carbon element on thesurface, that is anode current collector 3 side, of electrode layer 1.Similarly, fluoride ion battery 10 may comprise anode active materiallayer 5 containing a simple substance of the second metal element on asurface, that is anode current collector 3 side, of solid electrolytelayer 2. Also, by charging fluoride ion battery 10 shown in FIG. 1A,fluoride ion battery 10 shown in FIG. 1B may be obtained. Meanwhile, bydischarging fluoride ion battery 10 shown in FIG. 1B, fluoride ionbattery 10 shown in FIG. 1A may presumably be obtained.

The fluoride layer is a layer that contains a fluoride of the firstmetal element or the carbon element included in the electrode layer, andcorresponds to a charged cathode active material layer. The thickness ofthe fluoride layer varies with the state of charge, and thus notlimited. Also, the completely discharged electrode layer (such aselectrode layer 1 in FIG. 1A) preferably has a uniform composition. Inparticular, a current collector portion in which fluorination reactiondoes not occur and an active material portion in which fluorinationreaction and defluorination reaction have occurred preferably haveatomic continuity. Whether the atomic continuity is present or not maybe, for example, confirmed by observing the interface by a transmissionelectron microscope.

The anode active material layer is a layer containing a simple substanceof the second metal element, and usually generated from the solidelectrolyte layer in a self-forming manner. The thickness of the anodeactive material layer varies with the state of charge, and thus notlimited. Also, the anode active material layer (such as anode activematerial layer 5 in FIG. 1B) preferably contains a residual component ofthe solid electrolyte material in addition to a simple substance of thesecond metal element. The residual component refers to, among theelements included in the solid electrolyte material, a componentincluding an element other than the second metal element deposited as asimple substance of metal. For example, in the later described Examples,at the time of charge, a reaction ofLa_(0.9)Ba_(0.1)F_(2.9)+2.7e⁻→0.9La+0.1BaF₂+2.7F⁻ occurred. In thiscase, the La corresponds to a simple substance of the second metalelement, and BaF₂ corresponds to the residual component. The residualcomponent is preferably a metal fluoride.

3. Anode Current Collector

The anode current collector in the present disclosure collects currentsof the anode active material. Examples of the anode current collectormay include metal current collectors including metal elements, andcarbon current collectors including carbon elements. Examples of themetal current collector may include a simple substance and an alloy.Examples of the metal element to be used in the metal current collectormay include Au, Ag, Pt, Pd, Ph, Ir, Ru, and Os. Also, the metal elementto be used in the metal current collector may be the above describedfirst metal element. Meanwhile, examples of the carbon current collectormay include graphite and graphene.

Also, the anode current collector may be the same member as theelectrode layer. In this case, just two members: the electrode layer(anode current collector) and the solid electrolyte layer, may functionas 5 members: a cathode current collector, a cathode active materiallayer, an electrolyte layer, an anode active material layer, and ananode current collector. As the result, reduction in the cost of abattery may be achieved.

Examples of the shape of the anode current collector may include a foilshape. The thickness of the anode current collector is, for example, 5μm or more, and may be 10 μm or more. Meanwhile, the thickness of theanode current collector is, for example, 100 μm or less, and may be 50μm or less. Also, considering the corrosion due to fluorination, anauxiliary current collector with high chemical stability may be arrangedin addition to the anode current collector. Examples of the auxiliarycurrent collector may include current collectors including noble metalssuch as Au and Pt.

4. Fluoride Ion Battery

The fluoride ion battery of the present disclosure is provided with theabove described electrode layer, solid electrolyte layer, and anodecurrent collector. The fluoride ion battery may further comprise amonopolar structure including a single electrode layer and solidelectrolyte layer, or may further comprise a bipolar structure in whicha plurality of the electrode layers and the solid electrolyte layers arealternately disposed. In the latter case, increase in the voltage of abattery may be achieved.

FIGS. 2A and 2B are schematic cross-sectional views exemplifying thefluoride ion battery of the present disclosure; FIG. 2A shows the statebefore charge, and FIG. 2B shows the state after charge. Fluoride ionbattery 10 shown in each FIGS. 2A and 2B comprises: electrode layer 1that includes a first metal element of a carbon element and hascapability of fluorination and defluorination; solid electrolyte layer 2containing a solid electrolyte material, the solid electrolyte materialincluding a second metal element with lower fluorination potential anddefluorination potential than the potentials of the first metal elementor the carbon element; and anode current collector 3, in this order inthe thickness direction; and further comprises a bipolar structure inwhich a plurality of electrode layers 1 and solid electrolyte layers 2are alternately disposed.

Also, for example, as shown in FIG. 2A, electrode layers 1 may bedirectly disposed on the both surfaces of solid electrolyte layers 2 inthe bipolar structure. Also, for example, as shown in FIG. 2B, fluorideion battery 10 may comprise fluoride layers 4 containing fluorides ofthe first metal element or the carbon element on surfaces, that areanode current collectors 3 side, of electrode layers 1, in the bipolarstructure, and may comprise anode active material layers 5 containing asimple substance of the second metal element on surfaces, that are anodecurrent collectors 3 side, of solid electrolyte layers 2, in the bipolarstructure.

In the bipolar structure, the electrode layer at the end (such aselectrode layer 1 positioned at the top in FIGS. 2A and 2B) functions asa cathode current collector and a cathode active material layer.Meanwhile, the electrode layer sandwiched by solid electrolyte layers(such as electrode layer 1 positioned in the second from the top inFIGS. 2A and 2B) functions as an intermediate current collector and acathode active material layer. When an electrode layer and a solidelectrolyte layer is counted as a structural unit, the number of thestructural unit in the bipolar structure is, for example, 2 or more, andmay be 10 or more. Meanwhile, the number of the structural unit in thebipolar structure is, for example, 100 or less.

Here, among fluoride ion all solid batteries using metal activematerials, it is considered that the battery using Cu in the cathodeactive material layer and using La or Ce in the anode active materiallayer may function at the highest potential; however, the batteryvoltage is approximately 3 V, which is lower than that of theconventional lithium ion all solid batteries. Accordingly, when increasein a battery voltage is intended, it is necessary to increase the numberof cells to be connected in series. Meanwhile, considering the corrosiondue to fluorination, it is highly necessary to use a noble metal such asAu and Pt as a cathode current collector. From these points, whenincrease in a battery voltage is intended, the use of noble metals ispresumably increased as well.

In contrast, when the bipolar structure is applied for a battery, theuse of noble metals may be reduced while intending to increase thebattery voltage. As shown in the above described FIG. 2B, the electrodelayer sandwiched by solid electrolyte layers functions as anintermediate current collector so that the usage of noble metals is notmandatory; thus, the use of noble metals may be reduced. As the result,reduction in the cost of a battery may be achieved. Also, since noblemetals are relatively heavier than the other elements, the energydensity per battery weight may be increased by reducing the use of noblemetals.

The fluoride ion battery of the present disclosure is usually asecondary battery, so as to be repeatedly charged and discharged, and beuseful as a car-mounted battery for example. Incidentally, the secondarybattery includes a usage of a secondary batter as a primary battery (theuse for the purpose of just one time discharge after charge). Also,examples of the shape of the fluoride ion battery may include a coinshape, a laminate shape, a cylindrical shape, and a square shape. Also,the battery case to be used for the fluoride ion battery is not limited.

B. Method for Producing Fluoride Ion Battery

FIGS. 3A to 3D are the schematic cross-sectional views illustrating themethod for producing the fluoride ion battery of the present disclosure.In FIGS. 3A to 3D, firstly prepared is electrode layer 1 that includes afirst metal element or a carbon element and has capability offluorination and defluorination (FIG. 3A). Next, a solid electrolytematerial including a second metal element with lower fluorinationpotential and defluorination potential than the potentials of the firstmetal element or the carbon element, is directly disposed on one surfaceof electrode layer 1 and pressed so as to form solid electrolyte layer 2(FIG. 3B). Next, anode current collector 3 is directly disposed on thesurface, that is opposite to electrode layer 1, of solid electrolytelayer 2, and pressed (FIG. 3C). In this manner, a laminated bodyincluding electrode layer 1, solid electrolyte layer 2, and anodecurrent collector 3 in this order is formed; thereby, fluoride ionbattery 10 before charge may be obtained. Further, optionally, theobtained laminated body (fluoride ion battery 10 before charge) ischarged, fluoride layer 4 containing a fluoride of the first metalelement or the carbon element is formed on a surface, that is anodecurrent collector 3 side, of electrode layer 1, and anode activematerial layer 5 containing a simple substance of the second metalelement is formed on a surface, that is anode current collector 3 side,of solid electrolyte layer 2. Thereby, fluoride ion battery 10 aftercharge may be obtained.

According to the present disclosure, a fluoride ion battery, of whichpower generating elements may be formed by the combination of thespecific electrode layer and solid electrolyte layer, may be obtained.

The method for producing the fluoride ion battery of the presentdisclosure will be described by each step.

1. Laminated Body Forming Step

The laminated body forming step in the present disclosure is a step offorming a laminated body including: an electrode layer that includes afirst metal element or a carbon element and has capability offluorination and defluorination; a solid electrolyte layer containing asolid electrolyte material, the solid electrolyte material including asecond metal element with lower fluorination potential anddefluorination potential than the potentials of the first metal elementor the carbon element; and an anode current collector, in this order;and an anode active material layer being not present between the solidelectrolyte layer and the anode current collector. The electrode layer,the solid electrolyte layer, the anode current collector and the othermembers are respectively in the same contents as those described in “A.Fluoride ion battery” above; thus, the descriptions herein are omitted.

The method for producing the laminated body is not limited, and anarbitrary method may be applied. For example, the solid electrolytelayer may be stacked on the electrode layer, and the anode currentcollector may be stacked thereafter; and the solid electrolyte layer maybe stacked on the anode current collector, and then the electrode layermay be stacked thereafter. Also, the solid electrolyte layer may beproduced and thereafter one of the electrode layer and the anode currentcollector may be stacked followed by stacking the other; and the solidelectrolyte layer may be produced and thereafter the electrode layer andthe anode current collector may be stacked at the same time. Also, whenthe fluoride ion battery has the bipolar structure, for example, thebipolar structure may be formed by producing a member in which the solidelectrolyte layer is stacked on the electrode layer, and stacking themember plurality of times. Incidentally, it is preferable to press uponstacking each member and producing the solid electrode layer asrequired.

2. Charging Step

In the present disclosure, the method may further comprise a chargingstep of charging the laminated body, forming a fluoride layer containinga fluoride of the first metal element or the carbon element on asurface, that is the anode current collector side, of the electrodelayer, and forming an anode active material layer containing a simplesubstance of the second metal element on a surface, that is the anodecurrent collector side, of the solid electrolyte layer. The conditionsfor charging may be appropriately selected depending on factors such asthe members included in the fluoride ion battery.

3. Fluoride Ion Battery

The fluoride ion battery to be obtained by the method above is in thesame contents as those described in “A. Fluoride ion battery” above;thus, the description herein is omitted.

Incidentally, the present disclosure is not limited to the embodiments.The embodiments are exemplification, and any other variations areintended to be included in the technical scope of the present disclosureif they have substantially the same constitution as the technical ideadescribed in the claim of the present disclosure and offer similaroperation and effect thereto.

EXAMPLES

The present disclosure will be described in more details with referenceto Examples.

Example 1

Production of Solid Electrolyte Material

LaF₃ and BaF₂ were weighed so as to be LaF₃:BaF₂=9:1 in the molar ratio,and crushed and mixed by ball milling at 600 rpm for 12 hours. Afterthat, the obtained mixture was heat treated at 600° C. for 10 hours inan Ar atmosphere to obtain La_(0.9)Ba_(0.1)F_(2.9).

Production of Evaluation Cell

Powder La_(0.9)Ba_(0.1)F_(2.9) of 200 mg was placed on a Pb foil(electrode layer) and subjected to pressure powder molding so as toobtain a pellet. Three of the obtained pellets were stacked, a Pt foil(anode current collector) was arranged, and the product was subjected topressure powder molding. A Pt foil (an auxiliary current collector) wasplaced on the surface, that is the cathode side, of the obtainedlaminated body, and thereby an evaluation cell was obtained.

[Evaluation]

A charge and discharge test was conducted for the evaluation cellobtained in Example 1. The conditions for the charge and discharge testwere: under the environment at 140° C., currency of 50 μA/cm², andvoltage of 0 V to 7 V. As shown in FIG. 4, by charging and dischargingthree cells stacked in series, a charge plateau was confirmed in thevicinity of 6.8 V, and a discharge plateau was confirmed in the vicinityof 5 V. The constitution of this evaluation cell is shown as follows:

Pt foil: auxiliary current collector;

Pb foil (the portion not in reaction with F⁻): cathode current collectoror intermediate current collector;

Pb foil (the portion in reaction with F⁻): cathode active material layer

Pb+2F⁻

PbF₂+2e⁻;

La_(0.9)Ba_(0.1)F_(2.9) (cathode current collector side): solidelectrolyte layer;

La_(0.9)Ba_(0.1)F_(2.9) (anode current collector side): anode activematerial layer

La_(0.9)Ba_(0.1)F_(2.9)+2.7e⁻

0.9La+0.1BaF₂+2.7F⁻;

Pt foil: anode current collector.

In this manner, two kinds of members: the electrode layer and the solidelectrolyte layer, formed the power generating elements (the cathodeactive material layer, the solid electrolyte layer, and the anode activematerial layer) of the battery, and a fluoride ion battery that actuallyoperated was obtained.

REFERENCE SIGNS LIST

-   1 electrode layer-   2 solid electrolyte layer-   3 anode current collector-   4 fluoride layer-   5 anode active material layer-   10 fluoride ion battery

What is claimed is:
 1. A fluoride ion battery utilizing only fluorideions as carrier and comprising: an electrode layer that includes a firstmetal element or a carbon element and has capability of fluorination anddefluorination; a solid electrolyte layer containing a solid electrolytematerial, the solid electrolyte material including a second metalelement with lower fluorination potential and defluorination potentialthan the potentials of the first metal element or the carbon element;and an anode current collector, in this order; and an anode activematerial layer being not present between the solid electrolyte layer andthe anode current collector; and the fluoride battery further comprisinga bipolar structure in which a plurality of the electrode layers and thesolid electrolyte layers are alternately and directly disposed.
 2. Thefluoride ion battery according to claim 1, wherein the anode currentcollector is directly disposed on a surface of the solid electrolytelayer.
 3. The fluoride ion battery according to claim 1, wherein theanode current collector is made of the same material as the electrodelayer.
 4. The fluoride ion battery according to claim 1, wherein thefirst metal element is at least one of Pb, Cu, Sn, In, Bi, Sb, Ni, Co,La, Ce, Mn, V, Fe, Cr, Nb, Ti, and Zn.
 5. The fluoride ion batteryaccording to claim 1, wherein the second metal element is at least oneof La, Ba, Pb, Sn, Ca, and Ce.
 6. The fluoride ion battery according toclaim 1, wherein the solid electrolyte material is at least one ofLa_(1-x)Ba_(x)F_(3-x) in which 0≤x≤2, Pb_(2-x)Sn_(x)F₄ in which 0≤x≤2,Ca_(2-x)Ba_(x)F₄ in which 0≤x≤2, and Ce_(1-x)Ba_(x)F_(3-x) in which0≤x≤2.
 7. The fluoride ion battery according to claim 1, wherein theanode current collector is a metal current collector or a carbon currentcollector.
 8. A fluoride ion battery utilizing only fluoride ions ascarrier and comprising: an electrode layer that includes a first metalelement or a carbon element and has capability of fluorination anddefluorination; a solid electrolyte layer containing a solid electrolytematerial, the solid electrolyte material including a second metalelement with lower fluorination potential and defluorination potentialthan the potentials of the first metal element or the carbon element;and an anode current collector, in this order; and a fluoride layercontaining a fluoride of the first metal element or the carbon elementon a surface, that is the anode current collector side, of the electrodelayer; and an anode active material layer containing a simple substanceof the second metal element on a surface, that is the anode currentcollector side, of the solid electrolyte layer; and the fluoride batteryfurther comprising a bipolar structure in which a plurality of theelectrode layers and the solid electrolyte layers are alternatelydisposed interposing the fluoride layer.
 9. The fluoride ion batteryaccording to claim 8, wherein the anode current collector is made of thesame material as the electrode layer.
 10. The fluoride ion batteryaccording to claim 8, wherein the first metal element is at least one ofPb, Cu, Sn, In, Bi, Sb, Ni, Co, La, Ce, Mn, V, Fe, Cr, Nb, Ti, and Zn.11. The fluoride ion battery according to claim 8, wherein the secondmetal element is at least one of La, Ba, Pb, Sn, Ca, and Ce.
 12. Thefluoride ion battery according to claim 8, wherein the solid electrolytematerial is at least one of La_(1-x)Ba_(x)F_(3-x) in which 0≤x≤2,Pb_(2-x)Sn_(x)F₄ in which 0 ≤x≤2, Ca_(2-x)Ba_(x)F₄ in which 0≤x ≤2, andCe_(1-x)Ba_(x)F_(3-x) in which 0≤x≤2.
 13. The fluoride ion batteryaccording to claim 8, wherein the anode current collector is a metalcurrent collector or a carbon current collector.
 14. A method forproducing a fluoride ion battery utilizing only fluoride ions as carrierand, the method comprising: a laminated body forming step of forming alaminated body including: an electrode layer that includes a first metalelement or a carbon element and has capability of fluorination anddefluorination; a solid electrolyte layer containing a solid electrolytematerial, the solid electrolyte material including a second metalelement with lower fluorination potential and defluorination potentialthan the potentials of the first metal element or the carbon element;and an anode current collector, in this order; and an anode activematerial layer being not present between the solid electrolyte layer andthe anode current collector; and further forming a bipolar structure inwhich a plurality of the electrode layers and the solid electrolytelayers are alternately and directly disposed.
 15. The method accordingto claim 14, further comprising a charging step of charging thelaminated body, forming a fluoride layer containing a fluoride of thefirst metal element or the carbon element on a surface, that is theanode current collector side, of the electrode layer, and forming ananode active material layer containing a simple substance of the secondmetal element on a surface, that is the anode current collector side, ofthe solid electrolyte layer.
 16. The method according to claim 14,wherein the anode current collector is a metal current collector or acarbon current collector.